Multi-length delivery system

ABSTRACT

A stent delivery system may comprise a shape memory metal bumper which is expandable from a reduced profile configuration to an increased profile configuration. The stent delivery system comprises an inner tube, a stent disposed about the inner tube and a shape memory metal bumper disposed about the inner tube adjacent the proximal end of the stent.

BACKGROUND OF INVENTION

[0001] A stent may be loaded onto a catheter inner tube either from thedistal end of the inner tube or from the proximal end of the inner tube.When the stent is loaded from the distal direction, however, the tip ofthe catheter may interfere with the stent. To avoid obstruction from thetip, the stent as loaded must have an opening wide enough to allowpassage of the tip therethrough which causes issues in deviceperformance. When the stent is loaded from the proximal direction, thestent may be obstructed by any proximal bumpers present on the innertube. Typically, a bumper is provided proximal to the stent receivingregion of the catheter inner tube to aid in delivering the stent fromthe catheter. To avoid obstruction from the bumper, the stent as loadedmust have an opening wide enough to allow passage of the bumpertherethrough, again causing issues with device performance.

[0002] Once the stent has been loaded on the catheter, a retractablesheath is typically placed over the stent. A number of devices forretracting a retractable sheath are known in the art. Patents disclosingretractable sheaths include U.S. Pat. No. 5,772,669 and U.S. Pat. No.5,868,755. With many retraction systems, it is necessary to move aportion of the manifold by a distance at least equal to the length ofthe loaded stent to retract the sheath.

[0003] While a number of patents such as U.S. Pat. No. 6,090,035, U.S.Pat. No. 6,01 8,857 and U.S. Pat. No. 5,911,452 have dealt with theissue of stent loading, there remains a need for innovative methods ofloading self-expanding stents onto catheters as well as for innovativecatheters that facilitate this stent loading. There also remains a needfor innovative catheters having retractable sheaths and sheathretraction mechanisms having a mechanical advantage to facilitate sheathretraction.

[0004] All US patents, patent applications and other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

[0005] Without limiting the scope of the invention, a brief summary ofvarious embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

[0006] A brief abstract of the technical disclosure in the specificationis provided as well only for the purposes of complying with 37 C.F.R.1.72. The abstract is not intended to be used for interpreting the scopeof the claims.

SUMMARY OF INVENTION

[0007] In one embodiment, the present invention is directed to a stentdelivery system comprising an inner tube having a proximal end and adistal end, a stent receiving region and a stent disposed about thestent receiving region of the inner tube. The delivery system furthercomprises a shape memory metal bumper disposed about the inner tube at aposition adjacent the proximal or distal end of the stent. Desirably,the stent receiving region is at the distal end of the inner tube andthe shape memory bumper is adjacent the proximal end of the stent.

[0008] The present invention is also directed in another embodiment to adelivery system for delivering an implantable medical device to a bodilylumen. The delivery system comprises an inner tube having a proximalend, a distal end and a medical device receiving region. An implantablemedical device is disposed about the medical device receiving region ofthe inner tube. A shape memory metal bumper is disposed about the innertube at a position adjacent the proximal or distal end of theimplantable medical device. Desirably, the medical device receivingregion is adjacent to the distal end of the inner tube and the shapememory bumper is adjacent the proximal end of the implantable medicaldevice.

[0009] The present invention is further directed to a device deliverysystem comprising an inner tube having a proximal end, a distal end anda medical device receiving region. Desirably, the medical devicereceiving region is adjacent to the distal end of the inner tube. Animplantable medical device is disposed about the medical devicereceiving region of the inner tube. A shape memory metal bumper isdisposed about the inner tube at a position adjacent to the distal endor more desirably, the proximal end of the implantable medical device.The shape memory metal bumper is transformable between a martensiticstate and an austenitic state. In the martensitic state, the shapememory metal bumper has a reduced profile. In the austenitic state, theshape memory metal bumper has an increased profile.

[0010] The present invention is also directed to a method of preparing astent delivery system. In accordance with the inventive method, a tubehaving a proximal end and a distal end is provided. The distal end ofthe tube terminates in an enlarged tip. The tube has a bumper formed ofa shape memory metal proximal to the tip. The bumper is expandable froma reduced profile state to an increased profile state. The bumper is inthe reduced profile state. A stent having a flow passage therethroughsized to allow passage of the bumper therethrough when the bumper is inthe reduced profile state is provided. The stent is passed about thebumper and the stent disposed about the inner tube adjacent to thebumper, between the bumper and the tip. Finally, the bumper is caused totransition from the reduced profile state to the increased profilestate.

[0011] In another embodiment, the invention is directed to a medicaldevice delivery system comprising a manifold having a rack and pinion.An inner tube extends distally from the manifold. A retractable sheathis disposed about the distal end of the inner tube. A pull-wire extendsproximally from the retractable sheath to the manifold. The pull wire isattached to the pinion. The sheath may be retracted by moving one of therack and pinion relative to the other.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 shows a side view of a medical device delivery systemaccording to the invention including a cross-sectional view of thedistal portion thereof and a side view of the proximal end showing themanifold portion thereof.

[0013]FIG. 2 shows a side elevational view of a bumper in a reducedprofile configuration disposed about an inner tube according to theinvention.

[0014]FIG. 3 is a cross-sectional view of the slotted portion of thebumper of FIG. 2.

[0015]FIG. 4 shows a side elevational view of a bumper in a partiallyexpanded configuration disposed about an inner tube according to theinvention.

[0016]FIG. 5 is a cross-sectional view of the slotted portion of thebumper of FIG. 4.

[0017]FIG. 6 shows a side elevational view of a bumper in an expandedprofile configuration disposed about an inner tube according to theinvention.

[0018]FIG. 7 is a cross-sect ional view of the slotted portion of thebumper of FIG. 6.

[0019]FIGS. 8a-c illustrate a process for loading a stent on a catheteraccording to the invention with the distal end of the catheter shown inlongitudinal cross-section.

[0020]FIG. 9 shows a side view of a manifold according to the inventionincluding a cross-sectional view of the distal end of the manifold.

[0021]FIG. 10 shows a gear for use with a pinion.

[0022]FIG. 11 shows a side view of a pinion.

[0023]FIG. 12 shows a rack.

[0024]FIG. 13 shows a side view of a manifold according to the inventionincluding a cross-sectional view of the distal end of the manifold.

[0025]FIG. 14 shows a side view of a manifold according to the inventionincluding a cross-sectional view of the distal end of the manifold.

[0026]FIG. 15 shows a top view of a manifold according to the inventionwith parts cut away.

[0027]FIG. 16 shows a side view of the manifold of FIG. 15 with partscut away.

DETAILED DESCRIPTION

[0028] While this invention may be embodied in many different forms,there are described in detail herein specific preferred embodiments ofthe invention. This description is an exemplification of the principlesof the invention and is not intended to limit the invention to theparticular embodiments illustrated.

[0029] A medical device delivery system is shown generally at 100 inFIG. 1. Medical device delivery system has a proximal end 102 and adistal end 104. Manifold 106 is provided at proximal end 102. Inner tube108 extends distally from manifold 106. The inner tube includes amedical device receiving region 110, desirably towards the distal end ofinner tube 108. Inner tube 108 terminates at the distal end in a tip112. Tip 112 may be integrally formed with the inner tube or may bebonded to the inner tube using any suitable bonding technique includingadhesive bonding, heat welding or laser bonding. A retractable sheath114 is disposed about the distal end of inner tube 108. Pull wire 116extends proximally from retractable sheath 114 to the region of manifold106. Retractable sheath 114 may be retracted by pulling pull wire 116 inthe proximal direction.

[0030] Medical device delivery system 100 further comprises a shapememory metal bumper 118 disposed about the inner tube adjacent tomedical device receiving region 110. Desirably, the shape memory bumperis adjacent the proximal end of the medical device receiving region.Shape memory metal bumper 118 may be affixed to inner tube 108 using anysuitable adhesive or using any other suitable method for affixing abumper to a tube. Shape memory metal bumper is transformable between areduced profile configuration, as shown in greater detail in FIGS. 2-3and an increased profile configuration, as shown in greater detail inFIGS. 4-7. In the embodiment of FIGS. 2-7, shape memory metal bumper 18is in the form of a tube having a slotted portion 120 and a non-slottedportion 122. Shape memory metal bumper 118 is shown in FIGS. 4-5 as ittransitions from the reduced profile configuration to the increasedprofile configuration. Slotted portion 120 of tube 118 is partiallyopen. In FIGS. 6-7, slotted portion 120 of tube 118 is fully open. Inthe fully open configuration, the shape memory metal bumper mayoptionally extend radially outward from the inner tube to a distance inexcess of the stent.

[0031] Any of the medical device delivery systems disclosed herein mayalso be provided with two shape memory metal bumpers with one of theshape memory metal bumpers proximal to the medical device or stent andthe other shape memory metal bumper distal to the medical device orstent.

[0032] Shape memory metal bumpers having other shapes may also be used.For example, one or more arcuate shape memory metal bumpers which do notextend all the way around the inner tube may be used. More generally anyshape memory metal bumper of any shape may be used as long as the bumperhas a reduced profile configuration in which the bumper may be passedthrough the flow passage of a stent or other medical device and anincreased profile configuration in which it cannot pass through the flowpassage of a medical device such as a stent.

[0033] Shape memory metal bumper 118 may be made of any suitable,biocompatible shape memory metal. Examples of shape memory metals whichmay be used include nickel-titanium alloy, generically known as nitinol,copper- aluminum- nickel, copper-zinc-aluminum andiron-manganese-silicon alloys.

[0034] Desirably, the shape memory metal bumper will be made of Nitinol.Nitinol has two phase, a martensitic phase and an austenitic phase. Aslotted tube of Nitinol may be formed to a desired shape such as thatshown in FIGS. 6 and 7 and the shape heat set into position. The Nitinolmay then be cooled while maintaining its shape and then plasticallydeformed to a new shape such as that shown in FIGS. 2 and 3. Uponsubsequent heating, the metal will return to the shape it originally hadprior to plastic deformation at the cold temperature.

[0035] Medical device delivery system 100 may be used to deliver avariety of implantable medical devices including stents and vena cavafilters. It is noted that for the purposes of this disclosure, the termstent is understood to refer to stents, grafts, stent-grafts and otherexpandable prostheses. As shown in FIG. 1, stent 124 is disposed aboutmedical device receiving region 110 of inner tube 108. Stent 124 isdesirably a self-expanding stent. An example of a suitable stent for usewith the medical device delivery system is a shape memory metal stentsuch as the Scimed Radius™ stent disclosed in WO 96/26689.

[0036] The inventive medical device delivery systems may also bemodified for use with balloon expandable stents by providing aninflatable medical balloon in the medical device receiving region and aninflation lumen for supplying an inflation fluid to the balloon. Anexample of a medical device delivery system with a balloon is shown incommonly assigned U.S. Pat. No. 5,989,280.

[0037] The inventive medical device delivery systems described above maybe provided in an over-the-wire configuration, a rapid exchangeconfiguration or a fixed wire configuration. Examples of catheters withsuch configurations are disclosed in U.S. Pat. No. 5,980,533 and U.S.Pat. No. 5,957,930.

[0038] The present invention is also directed to a method of preparing adelivery system for delivering an implantable medical device. Inaccordance with the inventive method, as shown in FIG. 8a, a tube 108having a proximal end and a distal end is provided. The distal end oftube 108 terminates in an enlarged tip 112. Tube 108 has a bumper 118formed of a shape memory metal proximal to tip 118. Bumper 118 isexpandable from a reduced profile state to an increased profile state.An implantable medical device having a flow passage therethrough sizedto allow passage of the bumper in the reduced profile statetherethrough, such as stent 124, is provided. As further shown in FIG.8a, the implantable medical device is passed about the bumper in thereduced profile state 118 a and the implantable medical device disposedabout the inner tube adjacent to the bumper, between the bumper and thetip. Finally, the bumper is caused to transition from the reducedprofile state to a partially increased profile state 118 b as shown inFIG. 8b, and then to the fully increased profile state 118 c as shown inFIG. 8c.

[0039] The transitioning of the bumper to the increased profileconfiguration may be caused by increasing the temperature of the bumper.Where the bumper is made of a shape memory metal having a martensiticstate and an austenitic state with associated austenitic start andfinish temperatures, the temperature of the bumper may be increased to atemperature exceeding the austenitic start temperature thereby causingthe bumper to transition from the reduced profile state to the increasedprofile state. The specific type of Nitinol should be chosen such thatthe austenitic start or finish temperature is not so high that the tubewould be damaged by heating the bumper.

[0040] The inventive method may optionally further comprise the step ofproviding a manifold to the proximal end of the inner tube subsequent todisposing the medical device adjacent to the bumper. Moreover, themethod may optionally include the step of providing a retractable sheathabout the implantable medical device prior to or subsequent to disposingthe implantable medical device about the inner tube adjacent to thebumper.

[0041] The inventive method may be used in conjunction with a variety ofimplantable medical devices including stents.

[0042] In another embodiment, as shown in FIGS. 1 and 9, the inventionis directed to a medical device delivery system shown generally at 100comprising a manifold 106 with an inner tube 108 extending proximallytherefrom. A retractable sheath 114 is disposed about the distal end ofinner tube 108. A pull wire 116 extends proximally from retractablesheath 114 to manifold 106. Manifold 106 includes a rack 158 and pinion162. Rack 158 is movable in a proximal direction. Pinion 162, shown ingreater detail in FIGS. 10 and 11, includes a gear portion 170 having aplurality of teeth 172 disposed about the periphery and a shaft portion174 which serves as a spool for taking up the pull wire. Pinion 162 mayoptionally be provided with an enlarged end 176 to aid in retaining thepull wire on spool portion 174. Rack 158, as shown in FIG. 12, comprisesa plurality of teeth 178 arranged linearly thereon. As rack 158 is movedin the proximal direction, rack 158 engages pinion 162 and pull wire 116is wound around spool portion 174 of pinion 162 thereby retractingretractable sheath 114.

[0043] As the diameter of the spool portion of the pinion increasesrelative to the diameter of the gear portion, the mechanical advantageof the rack and pinion assembly increases reducing the length of racknecessary to retract the sheath by a fixed distance. While reducing thelength of rack is desirable in that it allows for a reduced lengthmanifold, if the mechanical advantage is excessive, the device willbecome more difficult to control as small, unintended displacements inthe rack will result in large displacements of the retractable sheath.Moreover, as the mechanical advantage is increased, the force necessaryto move the rack increases. Desirably, the ratio of the spool diameterto the gear diameter will range from 1:2 to 8:1 and more desirably, from1:1 to 4:1.

[0044] Manifold 106 comprises a first part 164 and a second part 166.First part 164 is movably received in second part 166. Rack 158 isattached to second part 166 while pinion 162 is attached to first part164. The invention also contemplates the use of manifolds with differentdesigns. For example, the rack and pinion may be mounted within aone-piece construction manifold. In such an embodiment, the rack wouldbe moved relative to the manifold itself to retract the retractablesheath.

[0045] Manifold 106 may, optionally, also slide in the distal direction.As the manifold slides in the distal direction, pull wire 116 unwindsfrom pinion 162. Desirably, a pull wire that is flexible enough to bewound and yet rigid enough to exert a pushing force to push theretractable sheath back into place as the pull wire unwinds will beused.

[0046] As shown in FIG. 13, the medical device delivery system may alsobe arranged, by altering the direction that the spool is wound, so thatretractable sheath 114 is retracted by sliding rack 158 in the distaldirection.

[0047] The embodiments of FIGS. 9 and 13 employ a spool which has aradius larger than that of the pinion to achieve a force advantage. Inanother embodiment, as shown in FIG. 14, the invention is directed to amedical device delivery system which employs a spool 174 having a radiussmaller than that of pinion 162 to achieve a distance advantage. Lessforce is required to retract the sheath, however, the rack must be moveda greater distance.

[0048] In the above embodiments, the pinion is fixed in place and therack is movable relative to the pinion. The invention also contemplatesembodiments in which the rack is fixed in place and the pinion ismovable relative to the rack. An example of such an embodiment is shownin FIGS. 15 and 16. FIG. 15 is a top view of a portion of a manifold 106in which rack 158 is fixed in place and pinion 162 is movable relativeto rack 158. FIG. 16 is a side view of manifold 106. Spindle 182 extendsoutward from pinion 162 through longitudinal slot 184 in manifold 106.Desirably, spindle 182 spins freely in pinion 162. As spindle 182 ismoved in a proximal direction, pinion 162 moves in a proximal directionwinding pull wire 116 around shaft portion 174 of pinion 162 therebyretracting in a proximal direction a retractable sheath (not shown)attached to the distal end of pull wire 116. The rack and pinion ofFIGS. 15 and 16 may also be arranged such that retraction of theretractable sheath results from moving the spindle in a distaldirection. The diameter of the shaft portion of the pinion may bealtered relative to the diameter of the gear portion to increase ordecrease the mechanical advantage of the device, as discussed above.

[0049] Where the inventive rack and pinion based medical device deliverysystem includes a bumper, the inventive shape memory bumper disclosedabove may be used or any other suitable bumper may be used.

[0050] The above disclosure is intended to be illustrative and notexhaustive. This description will suggest many variations andalternatives to one of ordinary skill in this art. All thesealternatives and variations are intended to be included within the scopeof the claims where the term “comprising” means “including, but notlimited to”. Those familiar with the art may recognize other equivalentsto the specific embodiments described herein which equivalents are alsointended to be encompassed by the claims.

[0051] Further, the particular features presented in the dependentclaims can be combined with each other in other manners within the scopeof the invention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below (e.g. claim 3 may be taken asalternatively dependent from claim 2; claim 4 may be taken asalternatively dependent on claim 1 or on claim 2; claim 5 may be takenas alternatively dependent from claims 2, 3 or 4; etc.).

1. A stent delivery system comprising: an inner tube having a proximalend, a distal end and a stent receiving region; a stent having aproximal end and a distal end, the stent disposed about the stentreceiving region of the inner tube; and a shape memory metal bumperdisposed about the inner tube adjacent the proximal or distal end of thestent.
 2. The stent delivery system of claim 1 wherein the shape memorybumper is adjacent the proximal end of the stent.
 3. The stent deliverysystem of claim 1 wherein the shape memory metal bumper has a firstreduced profile configuration and a second increased profileconfiguration, the shape memory metal bumper transformable from thefirst configuration to the second configuration.
 4. The stent deliverysystem of claim 3 wherein the shape memory metal bumper may betransformed from the first configuration to the second configuration byincreasing the temperature of the shape memory metal bumper.
 5. Thestent delivery system of claim 1 wherein the shape memory metal bumperis a tube having a slotted portion and a non-slotted portion.
 6. Thestent delivery system of claim 5 wherein the shape memory metal bumperhas a first reduced profile configuration and a second increased profileconfiguration, the shape memory metal bumper expandable from the firstconfiguration to the second configuration.
 7. The stent delivery systemof claim 6 wherein the slotted portion opens on expansion of the shapememory metal bumper.
 8. The stent delivery system of claim 6 wherein theslotted portion extends at a non-zero angle relative to the non-slottedportion on expansion of the shape memory metal bumper.
 9. The stentdelivery system of claim 1 further comprising a retractable sheathdisposed about the stent.
 10. The stent delivery system of claim 9wherein the stent is made of nitinol.
 11. The stent delivery system ofclaim 1 wherein the shape memory metal is nitinol.
 12. The stentdelivery system of claim 3 wherein the shape memory metal bumper in theincreased profile configuration extends radially outward from the innertube to a greater distance than the stent.
 13. A delivery system fordelivering an implantable medical device to a bodily lumen comprising:an inner tube having a proximal end and a distal end; an implantablemedical device having a proximal end and a distal end, the implantablemedical device disposed about a portion of the inner tube; and a shapememory metal bumper disposed about the inner tube adjacent the proximalor distal end of the implantable medical device.
 14. The delivery systemof claim 13 wherein the shape memory metal bumper is adjacent theproximal end of the implantable medical device.
 15. The delivery systemof claim 14 wherein the implantable medical device is selected from thegroup consisting of stents, stent-grafts, grafts and vena cava filters.16. A device delivery system comprising an inner tube having a proximalend and a distal end; an implantable medical device having a proximalend and a distal end, the implantable medical device disposed about aportion of the inner tube; and a shape memory metal bumper disposedabout the inner tube adjacent the proximal or distal end of theimplantable medical device, the shape memory metal bumper transformablebetween a martensitic state and an austenitic state, the shape memorymetal bumper having a reduced profile in the martensitic state and anincreased profile in the austenitic state.
 17. A method of preparing adevice for delivery of an implantable medical device comprising thesteps of: providing a tube having a proximal end and a distal end, thedistal end terminating in an enlarged tip, the tube having a bumperproximal to the tip, the bumper formed of a shape memory metal, thebumper expandable from a reduced profile state to an increased profilestate, the bumper in the reduced profile state; providing an implantablemedical device having a flow passage therethrough, the flow passagesized to allow the bumper in the reduced profile state to passtherethrough; passing the implantable medical device about the bumperand disposing the implantable medical device about the inner tubeadjacent to the bumper, between the bumper and the tip; causing thebumper to transition from the reduced profile state to the increasedprofile state.
 18. The method of claim 17 wherein the implantablemedical device is a stent.
 19. The method of claim 18 further comprisingthe step of providing a manifold to the proximal end of the inner tubesubsequent to the passing step.
 20. The method of claim 18 furthercomprising the step of providing a retractable sheath about the stent.21. The method of claim 20 further comprising the step of providing amanifold to the proximal end of the inner tube subsequent to the passingstep.
 22. The method of claim 20 wherein the retractable sheath isprovided about the stent subsequent to disposing the stent about theinner tube adjacent to the bumper, between the bumper and the tip. 23.The method of claim 20 wherein the retractable sheath is provided aboutthe stent prior to disposing the stent about the inner tube adjacent tothe bumper, between the bumper and the tip.
 24. The method of claim 18wherein the bumper is a tube having a slotted portion and a non-slottedportion.
 25. The method of claim 18 wherein the bumper is made ofnitinol.
 26. The method of claim 18 wherein the temperature of thebumper is increased during the causing step thereby causing the bumperto transition from the reduced profile state to the increased profilestate.
 27. The method of claim 18 wherein the shape memory metal bumperhas a martensitic state and an austenitic state, the bumper in themartensitic state being in the reduced profile state, the bumper in theaustenitic state being in the increased profile state.
 28. The method ofclaim 27 wherein the temperature of the shape memory bumper has anaustenitic start temperature and an austenitic finish temperature andthe temperature of the bumper is increased to a temperature exceedingthe austenitic start temperature during the causing step thereby causingthe bumper to transition from the reduced profile state to the increasedprofile state.
 29. The method of claim 28 wherein the shape memory metalbumper is made of nitinol.
 30. A medical device delivery systemcomprising: a manifold having a rack and pinion, the rack slidable in aproximal direction; an inner tube having a proximal end and a distalend, the inner tube extending distally from the manifold; a retractablesheath disposed about the distal end of the inner tube; and a pull-wireextending proximally from the retractable sheath to the manifold, thepull wire attached to the pinion.
 31. The medical device delivery systemof claim 30 wherein the rack is movable in a distal direction.
 32. Themedical device delivery system of claim 30 wherein the retractablesheath is retracted by moving the rack in the proximal direction. 33.The medical device delivery system of claim 30 wherein the retractablesheath is retracted by moving the rack in the distal direction
 34. Themedical device delivery system of claim 30 wherein the manifoldcomprises a first part and a second part, the first part movablyreceived in the second part, the pinion disposed in the first part andthe rack disposed in the second part.
 35. The medical device deliverysystem of claim 30 further comprising a stent disposed about the innertube and covered by the retractable sheath.
 36. The medical devicedelivery system of claim 30 wherein the pinion comprises a gear portionand a spool portion for taking up the pull wire.
 37. The medical devicedelivery system of claim 36 wherein the pull wire is wound around thespool portion when the rack is moved in a proximal direction.
 38. Themedical device delivery system of claim 30 wherein the pinion is movablein a proximal direction.
 39. The medical device delivery system of claim30 wherein the retractable sheath is retracted by moving the pinion inthe proximal direction.